III-nitride semiconductor light emitting device

ABSTRACT

The present disclosure relates to a III-nitride semiconductor light-emitting device including a substrate with a first groove and a second groove formed therein, the substrate including a first surface and a second surface opposite to the first surface, a plurality of III-nitride semiconductor layers including a first semiconductor layer formed over the first surface of the substrate, a second semiconductor layer formed over the first III-nitride semiconductor layer, and an active layer disposed between the first and second III-nitride semiconductor layers and generating light by recombination of electrons and holes, a first opening formed on the first groove, a second opening formed on the second groove, a first electrode electrically connected from the second surface to the first III-nitride semiconductor layer through the first groove, and a second electrode electrically connected from the second surface to the second III-nitride semiconductor layer through the second groove and the second opening.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of PCT Application No.PCT/KR2009/005492 filed on Sep. 25, 2009, which claims the benefit andpriority to Korean Patent Application No. 10-2008-0093969, filed Sep.25, 2008. The entire disclosures of the applications identified in thisparagraph are incorporated herein by reference.

FIELD

The present disclosure relates generally to a III-nitride semiconductorlight-emitting device, and more particularly, to an electrode structureof a nitride semiconductor light-emitting device. The nitridesemiconductor light-emitting device refers to a light-emitting devicesuch as a light-emitting diode including a compound semiconductor layercomposed of Al_((x))Ga_((y))In_((1-x-y))N (0≦x≦1, 0≦y≦1, 0≦x+y≦1), andmay further include a material composed of other group elements, such asSiC, SiN, SiCN and CN, and a semiconductor layer made of such materials.

BACKGROUND

This section provides background information related to the presentdisclosure which is not necessarily prior art.

FIG. 1 is a view of an example of a conventional III-nitridesemiconductor light-emitting device. The III-nitride semiconductorlight-emitting device includes a substrate 100, a buffer layer 200 grownon the substrate 100, an n-type nitride semiconductor layer 300 grown onthe buffer layer 200, an active layer 400 grown on the n-type nitridesemiconductor layer 300, a p-type nitride semiconductor layer 500 grownon the active layer 400, a p-side electrode 600 formed on the p-typenitride semiconductor layer 500, a p-side bonding pad 700 formed on thep-side electrode 600, an n-side electrode 800 formed on the n-typenitride semiconductor layer 300 exposed by mesa-etching the p-typenitride semiconductor layer 500 and the active layer 400, and aprotection film 900.

In the case of the substrate 100, a GaN substrate can be used as ahomo-substrate. A sapphire substrate, a SiC substrate or a Si substratecan be used as a hetero-substrate. However, any type of substrate thatcan have a nitride semiconductor layer grown thereon can be employed. Inthe case that the SiC substrate is used, the n-side electrode 800 can beformed on the surface of the SiC substrate.

The nitride semiconductor layers epitaxially grown on the substrate 100are usually grown by metal organic chemical vapor deposition (MOCVD).

The buffer layer 200 serves to overcome differences in lattice constantand thermal expansion coefficient between the hetero-substrate 100 andthe nitride semiconductor layers. U.S. Pat. No. 5,122,845 describes atechnique of growing an AlN buffer layer with a thickness of 100 to 500Å on a sapphire substrate at 380 to 800° C. In addition, U.S. Pat. No.5,290,393 describes a technique of growing an Al_((x))Ga_((1-x))N(0≦x<1) buffer layer with a thickness of 10 to 5000 Å on a sapphiresubstrate at 200 to 900° C. Moreover, PCT Publication No. WO/05/053042describes a technique of growing a SiC buffer layer (seed layer) at 600to 990° C., and growing an In_((x))Ga_((1-x))N (0<x≦1) thereon. Inparticular, there is provided with an undoped GaN layer with athickness_of 1 micron to several microns (μm) on the AlN buffer layer,the Al_((x))Ga_((1-x))N (0≦x<1) buffer layer or theSiC/In_((x))Ga_((1-x))N (0<x≦1) layer.

In the n-type nitride semiconductor layer 300, at least the n-sideelectrode 800 formed region (n-type contact layer) is doped with adopant. In a particular embodiments, the n-type contact layer is made ofGaN and doped with Si. U.S. Pat. No. 5,733,796 describes a technique ofdoping an n-type contact layer at a target doping concentration byadjusting the mixture ratio of Si and other source materials.

The active layer 400 generates light quanta by recombination ofelectrons and holes. For example, the active layer 400 containsIn_((x))Ga_((1-x))N (0<x≦1) and has a single layer or multi-quantum welllayers.

The p-type nitride semiconductor layer 500 is doped with an appropriatedopant such as Mg, and has p-type conductivity by an activation process.U.S. Pat. No. 5,247,533 describes a technique of activating a p-typenitride semiconductor layer by electron beam irradiation. Moreover, U.S.Pat. No. 5,306,662 describes a technique of activating a p-type nitridesemiconductor layer by annealing over 400° C. PCT Publication No.WO/05/022655 describes a technique of endowing a p-type nitridesemiconductor layer with p-type conductivity without an activationprocess, by using ammonia and a hydrazine-based source material togetheras a nitrogen precursor for growing the p-type nitride semiconductorlayer.

The p-side electrode 600 is provided to facilitate current supply to thep-type nitride semiconductor layer 500. U.S. Pat. No. 5,563,422describes a technique associated with a light-transmitting electrodecomposed of Ni and Au and formed almost on the entire surface of thep-type nitride semiconductor layer 500 and in ohmic-contact with thep-type nitride semiconductor layer 500. In addition, U.S. Pat. No.6,515,306 describes a technique of forming an n-type superlattice layeron a p-type nitride semiconductor layer, and forming alight-transmitting electrode made of indium tin oxide (ITO) thereon.

The p-side electrode 600 can be formed thick as to not transmit butrather to reflect light toward the substrate 100. This technique iscalled the flip chip technique. U.S. Pat. No. 6,194,743 describes atechnique associated with an electrode structure including an Ag layerwith a thickness over 20 nm, a diffusion barrier layer covering the Aglayer, a bonding layer containing Au and Al, and covering the diffusionbarrier layer.

The p-side bonding pad 700 and the n-side electrode 800 are provided forcurrent supply and external wire bonding. U.S. Pat. No. 5,563,422describes a technique of forming an n-side electrode with Ti and Al.

The optional protection film 900 can be made of SiO₂.

The n-type nitride semiconductor layer 300 or the p-type nitridesemiconductor layer 500 can be constructed as a single layer or asplural layers. Vertical light-emitting devices are introduced byseparating the substrate 100 from the nitride semiconductor layers usinga laser technique or wet etching.

FIG. 2 is a view of an example of a III-nitride semiconductorlight-emitting device described in PCT Publication No. WO/2008/026902.The III-nitride semiconductor light-emitting device includes a substrate110, a buffer layer 210, an n-type III-nitride semiconductor layer 310,an active layer 410, a p-type III-nitride semiconductor layer 510, ap-side electrode 610, a p-side bonding pad 710, a first n-side electrode810 a, a second n-side electrode 810 b, and an opening 910. Thesubstrate 110 is formed of sapphire and has a groove 120 formed therein.

The opening 910 is formed on the groove 120 along and through theplurality of III-nitride semiconductor layers 210, 310, 410 and 510, theoptional first n-side electrode 810 a is formed on the n-typeIII-nitride semiconductor layer 310 in the opening 910, and the secondn-side electrode 810 b is brought into contact with the n-typeIII-nitride semiconductor layer 310 through the groove 120, such thatthe III-nitride semiconductor light-emitting device becomes a verticallight-emitting device. Here, the optional first n-side electrode 810 aserves to ensure contact between the second n-side electrode 810 b andthe n-type III-nitride semiconductor layer 310.

The light-emitting device as described in PCT publication No.WO/2008/026902 has a disadvantage in that, since the groove 120 and theopening 910 penetrate through the light-emitting device, a material suchas epoxy may go up from the bottom of the light-emitting device duringfabrication of the package. This light-emitting device also has thedisadvantage that a process for bonding a wire to the p-side bonding pad710 is necessary during fabrication of the package, subsequentlyincreasing the size of the package because the bonded wire should besufficiently wrapped in order to be protected.

SUMMARY

This section provides a general summary of the disclosure, and is not acomprehensive disclosure of its full scope or all of its features.

There is provided herein a III-nitride semiconductor light-emittingdevice, including: a substrate with a first groove and a second grooveformed therein, the substrate including a first surface and a secondsurface opposite to the first surface; a plurality of III-nitridesemiconductor layers including a first III-nitride semiconductor layerformed over the first surface of the substrate and having a firstconductivity type, a second III-nitride semiconductor layer formed overthe first III-nitride semiconductor layer and having a secondconductivity type different from the first conductivity type, and anactive layer positioned between the first and second III-nitridesemiconductor layers and generating light by recombination of electronsand holes; a first opening formed on the first groove along theplurality of III-nitride semiconductor layers; a second opening formedon the second groove along the plurality of III-nitride semiconductorlayers; a first electrode electrically connected from the second surfaceof the substrate to the first III-nitride semiconductor layer in thefirst opening through the first groove; and a second electrodeelectrically connected from the second surface of the substrate to thesecond III-nitride semiconductor layer through the second groove and thesecond opening.

According to one aspect of the present disclosure, a III-nitridesemiconductor light-emitting device which includes the electrodes formedby plating can be provided.

According to another aspect of the present disclosure, a III-nitridesemiconductor light-emitting device which can be easily mounted duringfabrication of the package can be provided.

According to still another aspect of the present disclosure, aIII-nitride semiconductor light-emitting device which allows fabricationof a package of small size can be provided.

According to yet another aspect of the present disclosure foreignsubstances can be prevented from going up from the bottom of aIII-nitride semiconductor light-emitting device.

Further areas of applicability will become apparent from the descriptionprovided herein. The description and specific examples in this summaryare intended for purposes of illustration only and are not intended tolimit the scope of the present disclosure.

DRAWINGS

The drawings described herein are for illustrative purposes only ofselected embodiments and not all possible implementations, and are notintended to limit the scope of the present disclosure.

FIG. 1 is a view of an example of a conventional III-nitridesemiconductor light-emitting device.

FIG. 2 is a view of another example of a III-nitride semiconductorlight-emitting device disclosed in PCT Publication No. WO/2008/026902.

FIG. 3 is a view of an embodiment of a III-nitride semiconductorlight-emitting device according to the present disclosure.

FIG. 4 is a scanning electron microscope (SEM) image of a III-nitridesemiconductor light-emitting device according to the present disclosure.

FIG. 5 is another SEM image of a III-nitride semiconductorlight-emitting device according to the present disclosure.

Corresponding reference numerals indicate corresponding parts throughoutthe several views of the drawings.

DETAILED DESCRIPTION

The present disclosure will now be described in detail with reference tothe accompanying drawings.

FIG. 3 is a view of an embodiment of a III-nitride semiconductorlight-emitting device according to the present disclosure. TheIII-nitride semiconductor light-emitting device includes a substrate 10,a buffer layer 20, an n-type III-nitride semiconductor layer 30, anactive layer 40, a p-type III-nitride semiconductor layer 50, a p-sideelectrode 60, a first electrode 82, a second electrode 72, a thirdelectrode 80, a fourth electrode 70, a first opening 92, a secondopening 94, an optional protection film 96, and a protection film 98.

The substrate 10, which may be formed of sapphire, includes a firstsurface 12 and a second surface 14 opposite to the first surface 12 andhas a first groove 90 a and a second groove 90 b formed therein.

The buffer layer 20 is epitaxially grown on the first surface 12 of thesubstrate 10. The n-type III-nitride semiconductor layer 30 isepitaxially grown on the buffer layer 20 and has n-type conductivity.The active layer 40 is epitaxially grown on the n-type III-nitridesemiconductor layer 30 and generates light by recombination of electronsand holes. The p-type III-nitride semiconductor layer 50 is epitaxiallygrown on the active layer 40 and has p-type conductivity. The p-sideelectrode 60 is formed on the p-type III-nitride semiconductor layer 50and facilitates the current supply to the p-type III-nitridesemiconductor layer 50.

The first opening 92 is formed on the first groove 90 a along the bufferlayer 20, the n-type III-nitride semiconductor layer 30, the activelayer 40 and the p-type III-nitride semiconductor layer 50, and thesecond opening 94 is formed on the second groove 90 b along the bufferlayer 20, the n-type III-nitride semiconductor layer 30, the activelayer 40 and the p-type III-nitride semiconductor layer 50. The n-typeIII-nitride semiconductor layer 30 is provided with a step 32 in thefirst opening 92 to form the third electrode 80 thereon.

The optional protection film 96 is formed over the first opening 92 andthe p-side electrode 60 to protect the light-emitting device from theexterior or electrically insulate the same. The protection film 98 isformed on the second opening 94 to electrically insulate the bufferlayer 20, the n-type III-nitride semiconductor layer 30 and the activelayer 40 from the fourth electrode 70.

The third electrode 80 is formed on the step 32 to be in contact withthe n-type III-nitride semiconductor layer 30 and serves as a seed whenthe first electrode 82 is formed by plating.

The fourth electrode 70 is formed at an upper part 94 a of the secondopening 94 to be in contact with the p-side electrode 60 and serves as aseed when the second electrode 72 is formed by plating.

The first electrode 82 is connected from the second surface 14 of thesubstrate 10 to the third electrode 80 in the first opening 92 throughthe first groove 90 a. Here, the first electrode 82 is formed in thefirst groove 90 a to prevent foreign substances from going up from thebottom of the light-emitting device. In the meantime, since the firstelectrode 82 protrudes from the second surface 14 of the substrate 10,it is possible to mount the light-emitting device on the substrate 10for use in fabricating the package without special wire bonding.

The second electrode 72 is connected from the second surface 14 of thesubstrate 10 to the fourth electrode 70 through the second groove 90 band the second opening 94. At this time, the second electrode 72 isformed in the second groove 90 b to prevent foreign substances fromgoing up from the bottom of the light-emitting device. Meanwhile, sincethe second electrode 72 protrudes from the second surface 14 of thesubstrate 10, the light-emitting device can be mounted on the substrate10 for use in fabricating the package without special wire bonding.

Hereinafter, a method for fabricating the III-nitride semiconductorlight-emitting device according to the present disclosure will now bedescribed.

First, the grooves 90 a and 90 b are formed in the first surface 12 ofthe substrate 10 using a laser. When focused, the laser can form thegrooves 90 a and 90 b in various shapes such as circle, ellipse, orpolygons at a diameter of a few microns to a few hundreds of microns byusing a 355 nm wavelength. In addition, the depth of the grooves 90 aand 90 b can be adjusted from a few microns to a few hundreds of micronsby the energy of the laser or the like. As the substrate 10 is polishedfrom the second surface 14, the grooves 90 a and 90 b penetrate throughthe substrate 10.

Next, the buffer layer 20, the n-type III-nitride semiconductor layer30, the active layer 40, and the p-type III-nitride semiconductor layer50 are epitaxially grown on the first surface 12 of the substrate 10.Here, the growth conditions (including growth temperature, growth speed,and growth pressure, etc.) are controlled to prevent the lateral growth.That is, the opening 92 and 94 are formed on the grooves 90 a and 90 bin the growth conditions in which the lateral growth does not occur. Forexample, with respect to the n-type III-nitride semiconductor layer 30,when TMGa, NH₃ and SiH₄ are supplied by 365 sccm, 11 slm and 8.5 slm,respectively, and treated in the growth conditions such as a growthtemperature of 1050° C., a doping concentration of 3×10¹⁸/cm³ and apressure of 300 torr to 500 torr, about a 4-μm GaN layer is grown. Thusthe opening 92 and 94 can be formed (in this case, circular grooves 90 aand 90 b having a diameter of 30 μm are used).

Next, the p-side electrode 60 is formed on the p-type III-nitridesemiconductor layer 50. Then, the n-type III-nitride semiconductor layer30 is exposed. The step 32 is formed during this process. The n-typeIII-nitride semiconductor layer 30 may be exposed by dry etching, wetetching, or both. Accordingly, the third electrode 80 can be formed onthe step 32 to be connected to the n-type III-nitride semiconductorlayer 30. Meanwhile, the step 32 increases the contact area between then-type III-nitride semiconductor layer 30 and the first electrode 82 orthe third electrode 80, thereby facilitating the current supply. Thep-side electrode 60 may be formed after the etching process for exposingthe n-type III-nitride semiconductor layer 30.

Next, the protection film 98 is formed on the second opening 94. Here,the protection film 98 may be formed of photoresist, SiO_(x), SiN_(x),BCB, polyimide, etc. The optional protection film 96 may be formed atthe same time during this process.

Next, the third electrode 80 and the fourth electrode 70 are formed. Thethird electrode 80 and the fourth electrode 70 may be formed bysputtering, E-beam evaporation, thermal deposition, or the like. Thethird electrode 80 and the fourth electrode 70 may be formed of any oneselected from the group consisting of Ni, Au, Ag, Cr, Ti, Pt, Pd, Rh,Ir, Al, Sn, In, Ta, Cu, Co, Fe, Ru, Zr, W and Mo, or any combinationthereof.

During this process, as the second opening 94 is inclinedly formed, thefourth electrode 70 may be formed on the inclined part of the secondopening 94 as well as the upper part 94 a thereof. Here, the fourthelectrode 70 is formed at the upper part 94 a of the second opening 94so that plating can proceed from the fourth electrode 70 formed at theupper part 94 a of the second opening 94 to the second surface 14 of thesubstrate 10 using the fourth electrode 70 as a seed during the processfor forming the second electrode 72 by plating. As such, the secondelectrode 72 can be continuously formed without interruption. Moreover,the third electrode 80 is formed on the step 32 so that the firstelectrode 82 can be continuously formed from the step 32 of the firstopening 92 to the second surface 14 of the substrate 10 using the thirdelectrode 80 as a seed during the process for forming the firstelectrode 82 by plating.

Next, the second surface 14 of the substrate 10 is polished. Thesubstrate 10 is polished to at least the region in which the grooves 90have been formed, thereby exposing the grooves 90 formed from the firstsurface 12 of the substrate 10 to the outside. The process for polishingthe substrate 10 may be omitted when the grooves 90 penetrate throughthe first surface 12 and the second surface 14 of the substrate 10.

Next, the first electrode 82 and the second electrode 72 are formed byplating. The plating may be electroplating. According to theelectroplating, an object to be plated is connected to the negative (−)pole and a plating material is connected to the positive (+) pole. Here,the plating material is a solution containing metal ions of highelectric conductivity, such as Au, Ag, Cu, Al, etc. When the current isapplied to the solution containing metal ions of high electricconductivity, the reduction reaction occurs at the negative (−) pole andthe oxidation reaction occurs at the positive (+) pole. Here, the firstelectrode 82 and the second electrode 72 are formed of the metal ionscontained in the solution on the object to be plated which is connectedto the negative (−) pole due to the reduction reaction. Before theelectroplating, a protection film can be formed on parts other than theplating part to prevent plating. The protection film may be a blue tapeor the like.

FIG. 4 is an SEM image of the III-nitride semiconductor light-emittingdevice according to the present disclosure, particularly, a profile ofthe light-emitting device showing the first electrode (82; referring toFIG. 3). Hereinafter, an example of the electroplating will now bedescribed.

The electroplating was performed using Cu as a plating material.According to the electroplating, the light-emitting device to be platedwas connected to the negative (−) pole and Pt or phosphorized Cu (P:0.04% to 0.06%) was connected to the positive (+) pole. Here, anelectrolyte solution used was a sulfuric-acid-based solution and mightbe a general plating solution or a self-prepared solution.

The plating temperature was maintained at 20° C. If the platingtemperature is over 30° C., the plating surface may be roughened, theplating attachment may be reduced, and the protective film adhesiveness,such as the adhesiveness of blue tape, may be weakened.

The current was maintained at 150 mA. If a higher current is applied, itis difficult to achieve uniform plating. Moreover, for smooth plating,the plating solution was made to continuously flow, and thelight-emitting device was made to move in a circle.

In the above example, the electroplating time was about 95 min.

FIG. 5 is another SEM image of the III-nitride semiconductorlight-emitting device according to the present disclosure, particularly,the second surface (14: referring to FIG. 3) of the substrate (10:referring to FIG. 3) of the light-emitting device from which theelectrodes protrude outwardly.

Hereinafter, variety examples of the present disclosure are explained.

(1) The III-nitride semiconductor light-emitting device furthercomprising a protection film disposed on the first opening andelectrically insulating the first electrode from the plurality ofIII-nitride semiconductor layers except the first III-nitridesemiconductor layer.

(2) The III-nitride semiconductor light-emitting device furthercomprising a protection film disposed on the second opening andelectrically insulating the second electrode from the plurality ofIII-nitride semiconductor layers except the second III-nitridesemiconductor layer.

(3) The III-nitride semiconductor light-emitting device furthercomprising a third electrode disposed between the first III-nitridesemiconductor layer and the first electrode in the first opening andelectrically connected to the first III-nitride semiconductor layer andthe first electrode.

(4) The III-nitride semiconductor light-emitting device furthercomprising a fourth electrode disposed between the second III-nitridesemiconductor layer and the second electrode and electrically connectedto the second III-nitride semiconductor layer and the second electrode.

(5) The III-nitride semiconductor light-emitting device wherein thefirst opening and the second opening are formed by the first groove andthe second groove during the growth of the plurality of III-nitridesemiconductor layers.

(6) The III-nitride semiconductor light-emitting device wherein thesubstrate is formed of sapphire.

(7) The III-nitride semiconductor light-emitting device wherein theplurality of III-nitride semiconductor layers comprise a buffer layerepitaxially grown on the first surface of the substrate, an n-typeIII-nitride semiconductor layer epitaxially grown on the buffer layer, ap-type III-nitride semiconductor layer epitaxially grown on the n-typeIII-nitride semiconductor layer, and an active layer disposed betweenthe n-type and p-type III-nitride semiconductor layers and generatinglight by recombination of electrons and holes.

(8) The III-nitride semiconductor light-emitting device comprising: ap-side electrode formed on the p-type III-nitride semiconductor layer; athird electrode formed on the n-type III-nitride semiconductor layerexposed by etching the p-type III-nitride semiconductor layer and theactive layer; and a fourth electrode electrically connected to thep-side electrode, wherein the first electrode is electrically connectedfrom the second surface of the substrate to the third electrode in thefirst opening through the first groove, and the second electrode iselectrically connected from the second surface of the substrate to thefourth electrode through the second groove and the second opening.

(9) The III-nitride semiconductor light-emitting device comprising aprotection film formed on the second opening and electrically insulatingthe fourth electrode from the plurality of III-nitride semiconductorlayers except the p-type III-nitride semiconductor layer.

(10) The III-nitride semiconductor light-emitting device wherein thefirst electrode and the second electrode are formed to fill up thegrooves.

(11) The III-nitride semiconductor light-emitting device wherein thefirst electrode and the second electrode protrude from the secondsurface of the substrate.

The foregoing description of the embodiments has been provided forpurposes of illustration and description. It is not intended to beexhaustive or to limit the invention. Individual elements or features ofa particular embodiment are generally not limited to that particularembodiment, but, where applicable, are interchangeable and can be usedin a selected embodiment, even if not specifically shown or described.The same may also be varied in many ways. Such variations are not to beregarded as a departure from the invention, and all such modificationsare intended to be included within the scope of the invention.

The terminology used herein is for the purpose of describing particularexample embodiments only and is not intended to be limiting. As usedherein, the singular forms “a”, “an” and “the” may be intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. The terms “comprises,” “comprising,” “including,” and“having,” are inclusive and therefore specify the presence of statedfeatures, integers, steps, operations, elements, and/or components, butdo not preclude the presence or addition of one or more other features,integers, steps, operations, elements, components, and/or groupsthereof. The method steps, processes, and operations described hereinare not to be construed as necessarily requiring their performance inthe particular order discussed or illustrated, unless specificallyidentified as an order of performance. It is also to be understood thatadditional or alternative steps may be employed.

What is claimed is:
 1. A III-nitride semiconductor light-emittingdevice, comprising: a substrate with a first groove and a second grooveformed therein, the substrate including a first surface and a secondsurface opposite to the first surface; a plurality of III-nitridesemiconductor layers including a first III-nitride semiconductor layerformed over the first surface of the substrate and having a firstconductivity type, a second III-nitride semiconductor layer formed overthe first III-nitride semiconductor layer and having a secondconductivity type different from the first conductivity type, and anactive layer disposed between the first and second III-nitridesemiconductor layers and generating light by recombination of electronsand holes; a first opening formed on the first groove along theplurality of III-nitride semiconductor layers; a second opening formedon the second groove along the plurality of III-nitride semiconductorlayers; a first electrode electrically connected from the second surfaceof the substrate to the first III-nitride semiconductor layer in thefirst opening through the first groove; and a second electrodeelectrically connected from the second surface of the substrate to thesecond III-nitride semiconductor layer through the second groove and thesecond opening.
 2. The III-nitride semiconductor light-emitting deviceof claim 1, further comprising a protection film disposed on the firstopening and electrically insulating the first electrode from theplurality of III-nitride semiconductor layers except the firstIII-nitride semiconductor layer.
 3. The III-nitride semiconductorlight-emitting device of claim 1, further comprising a protection filmdisposed on the second opening and electrically insulating the secondelectrode from the plurality of III-nitride semiconductor layers exceptthe second III-nitride semiconductor layer.
 4. The III-nitridesemiconductor light-emitting device of claim 1, further comprising athird electrode disposed between the first III-nitride semiconductorlayer and the first electrode in the first opening and electricallyconnected to the first III-nitride semiconductor layer and the firstelectrode.
 5. The III-nitride semiconductor light-emitting device ofclaim 1, further comprising a fourth electrode disposed between thesecond III-nitride semiconductor layer and the second electrode andelectrically connected to the second III-nitride semiconductor layer andthe second electrode.
 6. The III-nitride semiconductor light-emittingdevice of claim 1, wherein the first opening and the second opening areformed by the first groove and the second groove during the growth ofthe plurality of III-nitride semiconductor layers.
 7. The III-nitridesemiconductor light-emitting device of claim 1, wherein the substrate isformed of sapphire.
 8. The III-nitride semiconductor light-emittingdevice of claim 1, wherein the plurality of III-nitride semiconductorlayers comprise a buffer layer epitaxially grown on the first surface ofthe substrate, an n-type III-nitride semiconductor layer epitaxiallygrown on the buffer layer, a p-type III-nitride semiconductor layerepitaxially grown on the n-type III-nitride semiconductor layer, and anactive layer disposed between the n-type and p-type III-nitridesemiconductor layers and generating light by recombination of electronsand holes.
 9. The III-nitride semiconductor light-emitting device ofclaim 8, comprising: a p-side electrode formed on the p-type III-nitridesemiconductor layer; a third electrode formed on the n-type III-nitridesemiconductor layer exposed by etching the p-type III-nitridesemiconductor layer and the active layer; and a fourth electrodeelectrically connected to the p-side electrode, wherein the firstelectrode is electrically connected from the second surface of thesubstrate to the third electrode in the first opening through the firstgroove, and the second electrode is electrically connected from thesecond surface of the substrate to the fourth electrode through thesecond groove and the second opening.
 10. The III-nitride semiconductorlight-emitting device of claim 9, comprising a protection film formed onthe second opening and electrically insulating the fourth electrode fromthe plurality of III-nitride semiconductor layers except the p-typeIII-nitride semiconductor layer.
 11. The III-nitride semiconductorlight-emitting device of claim 8, wherein the first electrode and thesecond electrode are formed to fill up the grooves.
 12. The III-nitridesemiconductor light-emitting device of claim 8, wherein the firstelectrode and the second electrode protrude from the second surface ofthe substrate.